One of the great "guilty pleasures" of 1980s TV was the 1981-89 series DYNASTY. Having seen the first season in reruns a while back, I've the sense that even then the producers hoped to create a spin-off by postulating that the Denver-based oil barons, the Carringtons, had a rival in another super-rich family, the Colbys. The two big families were bound in part by marriages between members, but it didn't seem to make them any more friendly over time.
The 1985 DYNASTY episode "The Titans" served to introduce the cast of the spinoff to the parent show's viewers prior to COLBYS's debut in November of that year. From then on the two shows didn't share many plotlines, and some of DYNASTY's actors , notably Joan Collins, refused to appear on COLBYS for fear of "weakening the brand," as some people call it these days. COLBYS started off with some powerhouse actors, particularly cinematic icons Charlton Heston and Barbara Stanwyck, both of whom certainly were more famous than John Forsythe and Linda Evans. Yet COLBYS never caught on and only lasted two seasons. I've not seen it in many years, but all I remember about it was a running plotline about incestuous desires between a brother and sister.
The crossover episode is okay fun, if one has a great tolerance for over-the-top line-deliveries and a wealth of scenes in which enemies bare their fangs at one another over champagne and studied innuendo. One of my first crossover-listings took a similar form, in that once the series ALL IN THE FAMILY was successful, its producer used not one but two episodes of that show as "back-door pilots" for his second series MAUDE. I'm not a big fan of the latter series, but I must admit that MAUDE by far a better spin-off than COLBYS. If COLBYS has any significance in a societal sense, it's probably just that the American public could only take so much champagne and caviar.